Double lumen catheters have been used as permanent blood access devices for easy and safe access to a patient's arteriovenous system for hemodialysis. Such double lumen catheters have been clinically used and commercially sold. One example of such double lumen catheters is disclosed in Mahurkar U.S. Pat. No. 4,568,329, with other examples of such catheters being disclosed as cited references in that patent.
The use of an indwelling hemodialysis catheter has significant advantages. Particularly, the patient does not have to endure a needle puncture to gain access to his arteriovenous system in every dialysis procedure, but, rather, the indwelling catheter can be simply periodically hooked up to the dialyzer system to provide a blood flow path between the patient and the dialyzer system.
However, as a disadvantage, indwelling catheters which connect to the arteriovenous system are subject to risks of infection and clotting.
Additionally, with a multiple lumen catheter, one lumen serves as a blood outflow path from the arteriovenous (A.V.) system and another lumen serves as an inflow passage for blood to be returned to the A.V. system. As a continuing problem with multiple lumen hemodialysis catheters, the suction at the entrance of the outflow port through which blood flows can cause the outflow port to be occluded by intimal tissues within the vein. This, in turn, can cause tissue damage and results in clotting, which has significantly limited the use of multiple lumen indwelling catheters for hemodialysis.
Furthermore, most multiple-lumen hemodialysis catheters are semi-rigid, with a result that they cannot be anchored securely, and consequently are prone to piston-like movements while they indwell a vein. This movement inside the vein tends to further irritate the intima of the vein wall tissue, leading to further clot formation and vein inflammation. Likewise, outward movements of the subcutaneous and external segments of such a catheter tend to collect contaminants, and to infect the subcutaneous tunnel through the tissue as these segments once again move inwardly.
Other hemodialysis catheters are more flexible, but are molded and cured in a generally straight configuration. Such catheters, however, are usually installed into the venous system in a substantially curved position. Thus, the elastic memory of these catheters causes them to press against some of the vein intima in certain places, with a resulting irritation thereof, and an increase in clotting potential. Likewise, it has been found that catheters which press against the vein walls also uncover vessel wall collage, which attract and activate platelets and the clotting system for an increase in clotting potential, which can cause catheter occlusion by clot attachment to the vein wall, subsequent fibrosis of the clot, and vein stenosis.
By this invention, a multiple-lumen, intravenous catheter, particularly for hemodialysis and also for any other desired use, is provided. The outflow port of the catheter, where a suction is developed, is protected against engagement with the vein intima tissues and the like.
Additionally, the catheter of this invention may be of a desired, curved configuration in its as-manufactured, unstressed configuration, so that the catheter occupies its indwelling site with less irritation of the vein or duct walls, wherever the catheter may be emplaced. The result of this is a catheter which is less likely to generate blood clotting or tissue irritation, and also with a reduction in its potential for causing infection. Such an indwelling catheter may thus be carried by a patient on hemodialysis for long-term use, providing the patient with relief from the anxiety and pain of the normal and frequent needle sticks that are required to accomplish hemodialysis with an A.V. fistula, and facilitating the hemodialysis procedure in other ways as well.